Patent Application
20130115561
The present invention generally involves a combustor and method for supplying fuel to a combustor.
Combustors are commonly used in industrial and power generation operations to ignite fuel to produce combustion gases having a high temperature and pressure. For example, gas turbines typically include one or more combustors to generate power or thrust. A typical gas turbine used to generate electrical power includes an axial compressor at the front, one or more combustors around the middle, and a turbine at the rear. Ambient air may be supplied to the compressor, and rotating blades and stationary vanes in the compressor progressively impart kinetic energy to the working fluid (air) to produce a compressed working fluid at a highly energized state. The compressed working fluid exits the compressor and flows through one or more nozzles into a combustion chamber in each combustor where the compressed working fluid mixes with fuel and ignites to generate combustion gases having a high temperature and pressure. The combustion gases expand in the turbine to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
Various design and operating parameters influence the design and operation of combustors. For example, higher combustion gas temperatures generally improve the thermodynamic efficiency of the combustor. However, higher combustion gas temperatures also promote flashback or flame holding conditions in which the combustion flame migrates towards the fuel being supplied by the nozzles, possibly causing severe damage to the nozzles in a relatively short amount of time. In addition, localized hot streaks in the combustion chamber may increase the disassociation rate of diatomic nitrogen, increasing the production of nitrogen oxides (NOX) at higher combustion gas temperatures. Conversely, lower combustion gas temperatures associated with reduced fuel flow and/or part load operation (turndown) generally reduce the chemical reaction rates of the combustion gases, increasing the production of carbon monoxide and unburned hydrocarbons.
In a particular combustor design, a plurality of tubes may be radially arranged in an end cap to provide fluid communication for the working fluid to flow through the end cap and into the combustion chamber. A fuel and/or a diluent may be supplied to the end cap and injected into the tubes to enhance mixing between the working fluid and fuel prior to combustion. The enhanced mixing between the working fluid and fuel prior to combustion reduces hot streaks in the combustion chamber that can be problematic with higher combustion gas temperatures. As a result, the tubes are effective at preventing flashback or flame holding and/or reducing NOX production, particularly at higher operating levels. However, an improved combustor and method for supplying fuel to the combustor that allows for staged fueling, multiple fuels, and/or diluents to be supplied to the tubes without obstructing the tubes would be useful.
Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.
One embodiment of the present invention is a combustor that includes an end cover and an end cap downstream from the end cover that extends radially across at least a portion of the combustor. The end cap includes an upstream surface axially separated from a downstream surface. A plurality of tubes extends from the upstream surface through the downstream surface to provide fluid communication through the end cap. An outer support tube extends downstream from the end cover and connects to the upstream surface of the end cap. An inner support tube extends downstream from the end cover and connects to the downstream surface of the end cap. A first plenum surrounds the inner support tube between the end cover and the upstream surface, and the first plenum extends radially between the upstream and downstream surfaces. A second plenum surrounds the first plenum between the end cover and the upstream surface, and the second plenum extends radially between the upstream and downstream surfaces.
Another embodiment of the present invention is a combustor that includes an end cover and a fuel conduit that extends downstream from the end cover. A downstream surface connected to the fuel conduit extends radially across at least a portion of the combustor. An upstream surface axially separated from the downstream surface extends radially across at least a portion of the combustor. A plurality of tubes extends from the upstream surface through the downstream surface to provide fluid communication through the upstream and downstream surfaces. A first plenum surrounds the fuel conduit between the end cover and the upstream surface, and the first plenum extends radially between the upstream and downstream surfaces. A second plenum that surrounds the first plenum between the end cover and the upstream surface, and the second plenum extends radially between the upstream and downstream surfaces.
The present invention may also include a method for supplying fuel to a combustor. The method includes flowing a working fluid through a plurality of tubes radially arranged in an end cap, wherein the end cap extends radially across at least a portion of the combustor. The method further includes flowing at least one of a first fuel or a first diluent through a first plenum, wherein the first plenum is at least partially defined by an inner support tube that connects to a downstream surface of the end cap, and flowing at least one of a second fuel or a second diluent through a second plenum that circumferentially surrounds at least a portion of the first plenum, wherein the second plenum is at least partially defined by an outer support tube that connects to an upstream surface of the end cap.
Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. In addition, the terms “upstream” and “downstream” refer to the relative location of components in a fluid pathway. For example, component A is upstream from component B if a fluid flows from component A to component B. Conversely, component B is downstream from component A if component B receives a fluid flow from component A.
Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Various embodiments of the present invention provide a combustor and method for supplying fuel to a combustor. The combustor generally includes a plurality of tubes radially arranged in an end cap to enhance mixing between a working fluid and fuel prior to combustion. In particular embodiments, an inner and an outer support may connect to the end cap, and multiple plenums may supply one or more fuels and/or diluents to the end cap to flow through the tubes. In other particular embodiments, a fuel conduit may connect to the end cap to support the end cap, and plenums surrounding the fuel plenum may supply one or more fuels and/or diluents to the end cap to flow through the tubes. In this manner, the various embodiments within the scope of the present invention may reduce flow disturbances through the tubes, increase structural support provided to the end cap, reduce manufacturing costs of the combustor, and/or enable staged fueling and/or multiple fuels and/or diluents to be supplied to the tubes over a wide range of operating conditions without exceeding design margins associated with flashback, flame holding, and/or emissions limits. Although exemplary embodiments of the present invention will be described generally in the context of a combustor incorporated into a gas turbine for purposes of illustration, one of ordinary skill in the art will readily appreciate that embodiments of the present invention may be applied to any combustor and are not limited to a gas turbine combustor unless specifically recited in the claims.
The end cap 18 may include an upstream surface 26 axially separated from a downstream surface 28, and a shroud 29 may surround the upstream and downstream surfaces 26, 28. A plurality of tubes 30 may extend axially from the upstream surface 26 to the downstream surface 28 to provide fluid communication through the end cap 18. The particular shape, size, number, and arrangement of the tubes 30 may vary according to particular embodiments. For example, the tubes 30 are generally illustrated as having a cylindrical shape; however, alternate embodiments within the scope of the present invention may include tubes having virtually any geometric cross-section. In addition, the tubes 30 may be radially arranged across the end cap 18 in one or more sets or groups of various shapes and sizes, with each set of tubes 30 having one or more separate fuel supplies. For example, multiple tubes 30 may be radially arranged around a fuel nozzle, or multiple sets of tubes 30 may be radially arranged across the end cap 18. One or more fluid conduits may provide one or more fuels, diluents, and/or other additives to each set of tubes 30, and the type, fuel content, and reactivity of the fuel and/or diluent may vary for each fluid conduit or set of tubes. In this manner, different types, flow rates, and/or additives may be supplied to one or more sets of tubes to enhance staged fueling of the tubes 30 over a wide range of operating conditions.
The combustor 10 may include one or more structures that extend downstream from the end cover 16 to support the end cap 18 and/or provide various fluid passages between the end cover 16 and the end cap 18. For example, as shown in
The outer support tube 42 may circumferentially surround the inner support tube 40 and connect to the upstream surface 26 of the end cap 18 to partially support the end cap 18 axially inside the combustor 10. In addition, the outer support tube 42 may define one or more fluid passages between the end cover 16 and the end cap 18. For example, as shown in
The first and second plenums 50, 52 provide fluid communication between the end cover 16 and the end cap 18 to allow various fuels, diluents, or other fluid additives to be supplied to the tubes 30. Each tube 30 in turn may include one or more ports 54 that provide fluid communication through the tube 30 from the first and/or second fuel plenums 50, 52. The ports 54 may be angled radially, axially, and/or azimuthally to project and/or impart swirl to the fluid flowing through the ports 54 and into the tubes 30. In addition, the particular number, size, and location of the ports 54 in the tubes 30 may be varied to allow staged fluid flow to the tubes 30. For example, as shown in
The combustor 10 may also include additional structures for supporting the end cap 18 and/or allowing thermal expansion between the various components. For example, as shown in the particular embodiment illustrated in
As further shown in
The various embodiments shown in
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
